1. By-product gypsum from various chemical industries as a retarder for the setting of cement;Murakami,1968
2. Partly-refined chemical by-product gypsums as cement additives;Erdogan;Cem. Concr. Res.,1994
3. Coal Combustion Product (CCP) Production and Use,2000
4. R. Kruger, South African Coal Ash Association, personal communication, Johannesburg, 2002.
5. K. Mathe, MSc Thesis, University of the Transkei, South Africa, 1996.